I am wanting to add power to my M416 type trailer and want to know if I wire up a charger/maintainer to the trailer battery and convert the trailer 4 way to the 7 pin to match my truck will it run the charger while I am driving? I also plan on using a 800 watt inverter when camping. I will mainly use it for lights and a tent fan for the summer

1. There is going to be a voltage drop in your wiring, so the deep cycle battery in the trailer/camper will not receive a full charge. You should "top off" your trailer battery charge with an external charger whenever it is practical and again before you store your trailer. [This will prevent an accumulation of lead sulfate and a premature loss of battery capacity.]

2. If the trailer battery is wired in parallel to your starting battery, isolate it by disconnect it from the towing vehicle when you are ready to use the trailer battery. [This is to keep starting battery from discharging, so you can restart your engine.]

3. For safety, fuse the wiring at the source and wire for more than the maximum output of the charging system and two percent (or less) voltage drop.

1. There is going to be a voltage drop in your wiring, so the deep cycle battery in the trailer/camper will not receive a full charge. You should "top off" your trailer battery charge with an external charger whenever it is practical and again before you store your trailer. [This will prevent an accumulation of lead sulfate and a premature loss of battery capacity.]

2. If the trailer battery is wired in parallel to your starting battery, isolate it by disconnect it from the towing vehicle when you are ready to use the trailer battery. [This is to keep starting battery from discharging, so you can restart your engine.]

3. For safety, fuse the wiring at the source and wire for more than the maximum output of the charging system and two percent (or less) voltage drop.

Thanks for the tips. Bought my battery yesterday and a new 7 pin connector. I need to cut the 4 pin and add wire for power and put all that into the 7 pin connector

The factory tow package had a 18ga. charge line. Because I have to run my rv trailer refrigerator on 12volts when I tow, I was running down my house battery on the trailer. The refrigerator on 12volts needed 13amps to operate, plus I wanted charge my trailer batteries as I tow.
I installed a 30amp circuit breaker off of my altenator,ran 8ga. wire back to the 7-pin connector, but the factory 7-pin was not set up for larger charge line wire , so I installed an aftermarket one and an aftermarket 7-pin pigtail for the trailer with heavier gauge wire. No voltage drop, runs refrigerator and charges two 12volt batteries on trailer! Next is to install 2 6volt golf cart batteries wired in series to get 12volts to double my AmpHours when I camp off-grid (boondock).

For now my fridge will stay in my truck and run of the truck battery. I want a battery set up for the trailer that will run some lights and a fan or blanket depending on the weather. I do no need anything to heavy duty right now. Plan on a battery and inverter for now

The factory tow package had a 18ga. charge line. Because I have to run my rv trailer refrigerator on 12volts when I tow, I was running down my house battery on the trailer. The refrigerator on 12volts needed 13amps to operate, plus I wanted charge my trailer batteries as I tow.
I installed a 30amp circuit breaker off of my altenator,ran 8ga. wire back to the 7-pin connector, but the factory 7-pin was not set up for larger charge line wire , so I installed an aftermarket one and an aftermarket 7-pin pigtail for the trailer with heavier gauge wire. No voltage drop, runs refrigerator and charges two 12volt batteries on trailer! Next is to install 2 6volt golf cart batteries wired in series to get 12volts to double my AmpHours when I camp off-grid (boondock).

Did you run that wire straight from the alternator to the rear 7-pin connector?

So I checked the voltage at the 7 pin today with the truck running and it read 13.8. I checked at the battery and the main fuse block. All the same readings. I thought it should be around 14.1 or am I wrong. If the voltage does not drop from the alternator to the connector is there really a need to run a dedicated wire? I have the factory tow package with 7 pin connector. My truck is a 2012 TRD OR 4x4

The factory 18ga wire should be good enough to charge the battery on the trailer. Because I tow with a refrigerator running on 12 volts pulling 13 amps the 18ga wire was not enough for the ampage I needed. I ran a seprate 8ga. wire from my altenator to a new 7-pin connector.

The factory 18ga wire should be good enough to charge the battery on the trailer. Because I tow with a refrigerator running on 12 volts pulling 13 amps the 18ga wire was not enough for the ampage I needed. I ran a seprate 8ga. wire from my altenator to a new 7-pin connector.

Yeah, no heavy duty charging needed for my set up. This is the first time I am doing anything like this so all the help is appreciated.

So I got my battery installed and changed the 4 flat plug to a seven pin plug. I ran a wire from the 7 pin aux power to the battery to charge while driving. My question is while it is charging does the negative terminal need to be grounded to the trailer?